prefixes within the in output graph

[marqh]

I think that it would aid readability of the output graphs if they were to include some RDF prefix definitions.

perhaps the bald prefix could be predefined.
by convention, we have wondered about the prefix this: for the identityURI
(added to opengeospatial/netcdf-ld#78 as a 'by convention')

aliases also represent an interesting and useful case. If an alias graph is provided at run time, could a prefix for this be derived?
would it be helpful to provide an explicit hook for alias graphs, such that the prefix could be specified, for example by picking up an rdfs:label from the top of the graph

very open to thoughts and ideas on this

some hints are presented in
opengeospatial/netcdf-ld#78
which could be amended based on this discussion

[simonoakesepimorphics]

The this: prefix has been implemented by #47 . It would take a little more effort to support assigning prefixes to alias files although this needs some design input to determine what the CLI input would be.